Electrical distribution system



Afiril 23, 1929.

F. GRIEB ELECTRICAL DISTRIBUTION SYSTEM 5 Filed Jan. 25, 1927 I T LED} Patented Apr. 23, 1929.

UNITED STATES PATENT OFFICE.

FRITZ GRIEB, 0F BADEN, SXVITZERLAND, ASSIGNOR SX JITZERLAND, A JOII'FT-STOCK COMPANY, OF SWITZER- BOVERI & CIE, OF BADEH, LAND.

TO AKTIENGESELLSCHAFTBROWN ELECTRICAL DISTRIBUTION SYSTEM.

Application filed January 25, 192?, Serial No.

My invention relates to electrical distribution systems and it has particular relation to an arrangement for controlling the voltage of two alternating-current systems which are interconnected by means of a transformer.

Among the objects of the invention is the provision of a system of the above character provided with means for adjusting the voltage of one system independently of that of the other system without requiring complicated tap-changing apparatus, switching arrangements, or other complicated mechanisms, such as used heretofore.

According to the invention the voltage on one side of a transformer is controlled independently of that of the other side of the transformer by providing an independent control of the excitation of the transformer core. The transformer is arranged so as to include 'a relatively large reactance in the connections to the network with respect to which it is to be independent, and any voltage difference between the networks that are to be interconnected by the transformer is taken care of by the voltage drop in the series reactance, said voltage drop being determined by the amount of excitation supplied to the transformer through the independent exitation control.

The foregoing and other objects of the invention. will be best understoodfrom the accompanying drawings in which Fig. l is a diagrammatic illustration of a distribution system embodying the invention;

Fig. 2 is a diagram similar to Fig. l illustrating another form of the invention; and

Fig. 3 is an explanatory vector diagram referred to hereinafter.

In general. it is not possible to regulate or independently adjust the primary and secondary voltages of a transformer, or the transformer ratio, without in some way de creasing or increasing the number of effective turns of the windings. The voltage ratio is fixed by the ratio of the turns. The only way which seemed heretofore practicable for varying the ratio consisted in adjusting the relative number of the turns in the primary and secondary windings of the transformer. Such system of regulation has serious disadvantages. It requires regulating switches and switching contacts; a particular type of winding distribution on the transformer with special taps and lead connections; and above 163,511, and in Switzerland January 30, 1926.

all, it requires special arrangements for permitting carrying out the switching operations while the transformer windings are carrying current, so as to prevent short-circuitmgof the transformer, and at the same time avoid interruption of the currentflovi therethrough. These special switching arrange ments are not only very expensive. but are, in addition, complicated and subject to damage and are accordingly very undesirable.

According to the invention a much more satisfactory system of regulation of the voltage ratio is obtained by controlling theexitation of the transformer, and'thereby varying the voltage drop between the transformer and the network with respect to which it is to be independent. To this end, the transformer may be provided with a large leakage and a variable voltage component may be inected between the two systems bymeans of a synchronous condenser whiclris connected to the transformer so as to vary the exitation thereof. The synchronous condenser is so connected to the transformer as to maintain the voltage on one side thereof asdesired,

and absorb the voltage diflerencebetween the transformer and the other side thereof in the leakage reactance of the transformer with respect to said other side. Thus, for instance, the synchronous condenser may be directly connected to the side of the transformer, the voltage of which is to be regulated. If the voltage on the other side of the transformer is fixed and should be left undisturbed, the voltage of the system that is to be regulated will be determined by the excitation of the synchronous condenser. The difference between the voltages of the two systems is'then absorbed in the leakage reactance of the transformer. interconnecting the two systems. In such arrangements the leakage-reactance voltage drop may assume considerable value and the vector diagram of the voltages must then conform to the requirement that not two, but three voltage components shall give 'a resultant equal to zero.

An arrangement of such character utilizing a synchronous condenser connected to one side of a transformer for independent regu-- lation of the voltage on one side of the transformer from that of the other side, and de-' pending on the large leakage reactance between the two transformer halves for this regulation, is shown m Fig. 1. An alternating-current network system I shown ennncctcd' 'to iii-I11,alternatiuggturrcnt network system II- -th rouglfatransformer '.l, ha ving a primary winding 1 and a secondary winding iconnccted to the two systems, respectiylyi' I; et usassumc that the alternating;-

current system I is a partof a large net\ that is to be maintained at a fixed voltage,

and that the voltage of this network ll remain fixed, and thatzthe. alternatilag-current:

denser as desired. 1 This control may be effected,

foninstanee by varying the current supplied to the exciting winding 6 of the synchronous i condenser through a regulator 7 whicnissultablysset' to secure the desired voltage control. Thezregulator 'l" .may, for instance -be arranged'to'beaetuated in response to't-hcvoltage-ofithe alternating-cu rent systemII, beingconnected to the terminals thereof. T he excitation currentafor the exciting winding 6-of the condenserzis shown'derived from an exciter-8 which'may be directly condenseqor arranged in any suitable mannen; By-varyi-rig'the excitation ofthe-field winding G-thevoltageacross the terminals ofthe synchronous condenser 6 may befvaried as desired,rand thereby the voltage of the alternating-current system II adjusted. The

"'- diiference of'the' voltage between the alterlow-leakage reactance.

voltage'regulation of nating current systems I and II is then covered bysthe leakage-'rcactance transformer T-, in cident to the flow of current through the transformer.

VVith "the foregoing system independent adjustment of thevoltages in the primary and secondary windings of the transformer-is obtained'by employing a transformer havinga large effective leakage flux and an adiustable synchronous condenser connected to the side of the transformer the voltage of which is to be regulated.

In many cases the transformer voltage which is to beregulated exceeds considerably the-voltage for which synchronous condenscrs, or-in general, rotating dynamoclectrie machines may be economically or conveniently' built; Accordingly, in many cases it is desirable' to use a three-winding transformer in which one of the windings has a much larger leal rage reactance than the other two windingsw-The line, the voltage of which is to beregulated, and the synchronous condenser are'then connected to the two windings with I The third winding with'high-leakagereactanee is connected to theother line which is to be unaffected by the the firstmentioned line.

driven by the drop in the An arrangement of such character is shown in- =F-ig. 2, in which the-transformer flginterconnecting the primary network 1 with the swondary network II has, in addition to the primary and secondary windings l. and 2,.respcctively; a tertiary winding 3 its terminals connected to" a "synchronouslcondenser 5. The synchronous condenser has an exciting winding (3 which is supplied from an exciter 8, the voltage: of: which is controlled by a regulator 10 to carryout any desired type of regulation of- 'the *voltage of the network II: In order tomahe the voltage of the secondary network'II independent of that of the primary network, the transformer T is so arranged that there is a relatively large-leakage reactan'ee between *the primaryiand secondary windings 1 and 2, and a relatively low-leakage i cactance between the secondary and the tertiarywindings 2 and 3. On account of the close coupling of the tertiary winding 3 with the secondary-winding 2, the voltage of thesynchronous machine 5 will determine the secondary {Volta-goof the transformer across the secondary network II, and this voltage-may be readily varied by changin g the excitation of the synchronous machine. The difference of the voltage between the primary and secondarynetwork is then covered by the" voltage d ro p in the leakage ary'network 2, maybe regulated to suit any particular operating requirements that may occur in practice: i For instance, itis sometimes desired to vary the voltage'of a'highvoltage transmission line 'independently of the voltage'of the power station from-which it is being supplied. Inother cases, it may be desirable to limit-in a predetermined manner, the flow of power-inra'tie line-interconnect ng two power stationscor two independently supplied networks. 1 In the latter case, an arrangement of'the foregoing character permits the control of the phase and magnitude of'the voltage in the tie line so as to secure the most favorable conditions with a minimum loss; In still other cases, it may be desirable to so control the voltage of the secondary network as to definitely limit the amount of power derived'from-the primary network and prevent thepower derived ther from through the transformer from exceed ing a predetermined value. In all such cases the regulator may bearranged to be automatically controlled in response to some electric quantity of the system in order to carry out the desired regulation.

The system shown in Fig. 2 illustrates, by way of example, the method of regulation arranged to so control the voltage of the second reactance between the transformer-windings- 1' and 2 incident to the flow 'of'current from a. regulating system,

ary network II as to prevent the load from the primary-network I from exceeding a predetermined value. To this end the regulator 10 is actuated inresponse to the combined ef-- fect of thevoltage across the primary network I, and the current fiowingin said network to the transformer "1, the voltage coil 11 of the connected across the priregulator to a current transformer 13. Fig. 3.gi vesa vector diagram illustrating an approximation of conditions-of the power exchange between the networks I and II when such as shown in'Fig. 2, iseemployed. r Assuming that 0.51 =6, is thevoltage of the primary network I and that thee'tfeetive pow- .er-transmitted to the network II shall remain constant, then the line m1n perpendicular to the vector e is theloc-us of the ends of the vectors i 11,, i representing the current flowing from the network I into the-transformer T. -For-thecasecorresponding to the flow of current represented by the vector 2', in phase with the primary voltage c there will be an inductive drop in the leakage reactance between the primary coil 1 and the secondary coil 2 of the transformer corresponding to the "ector A B, perpendicular to the voltage vector e The vector 0B =6 will then represent the voltage 0 across the secondary winding of the transformer. The voltage across the terminals of the synchronous condenser will then be of substantially the same phase as secondary voltage e corresponding to the vector =e Since the leakage between the primary and secondary windings 1 and 2 is much larger than that between the secondary and tertiary windings 2 and 3. the vector B0- e -e, will be much smaller that the vectorA B corresponding to the leakage drop between the primary and secondary windings. Corresponding to the different changes in the operating conditions, the excitation of. the synchronous condenser 5 is controlled by the regulatorlO so as to ca use the primary-current vectors i etc., to move along the line mm-. The end of the vector e corresponding to the voltage across the synchronous condenser, will then move on a line 00 perpendicular to the line m;4n, and the voltage vector 0 corresponding to the voltage across the secondary winding 2 of the transformer, will move along a line 11-11 parallel to 00. Thus, for the case of current i,, the condenser voltage is represented by the vector 6,, and the voltage across the secondary transformer winding b the vector a In every case the vectors A B and A B, etc, representing a voltage drop in the leakage rcactance between the primary and secondary windings of the transformer, will be perpendicular to the current vectors i i etc.

The system of regulation described hereinabove makes it possible to control the voltage the current coil :12 of the on one side of a transformer independently of that of the other side ofthe transformer,- without complicated and expensive switching or regulating devices. The new regulating system depends essentially-on the fact that by varying the excitation of a synchronous alternetting-current machine, such as asynchro nous condenser, it is-possible to control'the' voltage across one-side of. the transformer in dependently of that of the other side, the dif-- ference in voltage between the-two tra nsformer windings being absorbed by the dro in the leakage reacta-nce embodie l in the transform-.' er, or in the connections thereto; e

-'1. In an electrical distribution system comprising -a. primary network and a'secon'dary. network. and'a transformer interconnecting said networks. "said transformer I having" a fixed ratio of the primary winding to the sec'-- ondary' winding, means for controlling the voltage across one-winding of thetmnsformer without varying the voltage across the other winding thereof con'iprising asynchronous condenser 1 connected to the winding ofthe transformer, the" oltage. of whieh' 1is'to"'be regulated, said transformer embodying sutlicient reactance to absorb the voltage drop corresponding to the desired regulating range.

2. An electrical distribution system comprising a transformer having primary and secondary windings, primary and secondary alternating-current lines connected thereto, respectively, and means for controlling the voltage on one winding of the transformer, independently of that of the other winding thereof while maintaining substantially the same ratio of the turns'of the primary and secondary windings, said means comprising condenser means connected to the winding of the transformer the voltage of which is to be regulated.

3. An arrangement according to claim 2, comprising a. transformer having a tertiary winding connected to the synchronous condenser.

4. An electrical distribution system co n1- prising a primary network, a secondary network, a transformer comprising primary and secondary windings connected to said networks. respectively, said windings comprising relatively large reactance, and means for controlling the voltage on one winding of the transformer independently of that of the other winding without substantially varying the ratio of the turns of the primar 1 and secondary windings, said means comprising a tertiary winding having relatively close coupling with the transformer winding whose winding is to be independently controlled, a synchronous machine connected to said tertiary winding, and means for varying the excitation of said synchronous machine.

5. An electrical distribution system com prising a primary network, a secondary network, a transformer comprising primary and secondary windings connected to said networks, respectively,. saidv windings comprising relatively large reactanc-e, means-for controlling the voltage on one winding of the transformer independently of -:that of [the other winding without; substantially varying the ratio of the turns of the primary and sec-. ondary windings, said nieanscomprising a tertiary winding haying relatively; close .cou-

pling with the transformer wi-nding} whose. to: be independently controlled,-

transformerindependentlyof that of the other winding without substantially varyseeondary windings, saidmeans comprising a.

ing the ratio of-.:thei turns of the primary and spouse to the electrical-conditions=inoneof said networks. 7,: I 7 An alternatmgscuwent-distribution systemj comprising 2 a primary network, a secondary network, a tnansformer having- 'primary and: secondarywindings connected' to said network res'pectively,-fimeans for'z-comtrolling; the voltage of onewinding of said transformer independently of thati-of -stheother: winding .-,without a varying} the ratios of the turns oftheiprimary and secondaryawcind ings, said; means comprising :a synchronous machine associated with; the: winding 4 of the transformers-o be regulated; and imeans for; varying the excitationof said m'achine-.-: r V In' testimony iwher eof zlimawerzhereunto si ned my name-at-ZunichSwitZertand;ions this the :I-I-dayFof- January, 1 3ml); 1923. 

